Emperor Nero (37–68 AD) was a tyrant famous for his sexual appetites and tendency to execute anyone who challenged him (including his mother). The beautiful Poppaea Sabina became his mistress in around 58 AD. Nero made Poppaea’s husband Otho divorce her; he then divorced Octavia (whom he later had assassinated) and married Poppaea. Monteverdi keeps many of these sordid details, and follows the Roman historian Tacitus in depicting Poppea as a scheming minx and Nerone as a hedonistic bully. However, the couple’s exquisite duets (including ‘Pur ti miro’) add a romantic, even tender element to their relationship.

Gustav III of Sweden (1746–92) was an enlightened (if autocratic) monarch and a strenuous political reformer. On 16 March 1792 Jacob Johan Anckarström, a military captain, shot him at a masked ball. Verdi used this dramatic incident as the basis for Un ballo in maschera. However, the only ‘true’ elements of the opera are Gustav’s liberal patriotism, the foretelling of his death by the clairvoyant Ulrica Arfvidsson and the conspiracy between Anckarström and two noblemen. Gustav was no romantic, was never friends with Anckarström and likely never even met Anckarström’s wife. Nor did Gustav die immediately – he survived his assassination for nearly a fortnight before succumbing to septicaemia.

Hans Sachs (1494–1576) was a German shoemaker, playwright and Meistersinger – a member of a guild that organized competitions in poetry and song. He was extraordinarily productive, and wrote more than 6,000 literary works. Wagner stays true to life in making his Sachs a champion of the arts and leading Meistersinger. But Wagner’s Sachs is more pensive, less bawdy in humour and much more melancholy than the real Sachs – who was a widower for less than a year before taking a young second wife. Wagner also omits Sach’s love of animals: a contemporary portrait depicts him playing with a cat, with a dog asleep at his side.

André Chénier (1762–94) was a French poet and one of Robespierre’s last victims. His literary career was not particularly illustrious; he published just two poems in his lifetime and only became famous some twenty-five years after his death with the first edition of his collected poems. Though Chénier was a monarchist, his arrest was actually an accident (the officials believed they were arresting a marquis) and apparently he was only guillotined because Robespierre happened to remember a venomous political poem of his. Giordano and his librettist Luigi Illica transformed Chénier into a liberal idealist, and invented the character of Maddalena in order that he should have a great romance and a glorious, transfiguring death.

Elizabeth I, Robert Devereux, Robert Cecil, Walter Raleigh and others in Britten's Gloriana

Britten’s great historical opera explores the last years of Queen Elizabeth I (1533–1603) and her close relationship with the young, brilliant and unstable Robert Devereux, Earl of Essex (1565–1601). Inspired by literary biographies by Lytton Strachey and J.E. Neale, Britten and his librettist William Plomer stick fairly close to history, including such details as the Queen’s love of music and dancing and Essex’s unreliability as a military leader. The famous incident in Act III when Essex surprises the balding Queen dressing was also based on fact. However, in the interests of time they condensed Essex’s troubles on his return from Ireland, his rebellion and its aftermath.

Richard Nixon (1913–94) considered his 1972 visit to China to meet Mao Tse-tung (1893–1976) as ‘the week that changed the world’. John Adams and his librettist Alice Goodman based many details in their opera on fact: Mao’s charisma, at odds with his physical fragility; the premier Chou En-lai’s skills as a diplomat. But they also emphasize the most sympathetic aspects of the Nixons. Pat Nixon is gentle and idealistic, while Adams and Goodman came to see Richard Nixon as ‘a sort of Simon Boccanegra… self-doubting, lyrical’. By contrast Mao remains enigmatic, while his ambitious wife Chiang Ch’ing and Nixon’s advisor Henry Kissinger are the opera’s villains.

Un ballo in maschera runs until 17 January 2015. Tickets are sold out, but there are 67 day tickets for each performance and returns may become available.The production is a co-production with Theater Dortmund and Scottish Opera and is given with generous philanthropic support from The Royal Opera House Endowment Fund.

Andrea Chénier runs 20 January–6 February 2015. Tickets are still available, and there are 67 day tickets for each performance and returns may become available.The production is a co-production with the National Centre for the Performing Arts, Beijing, and San Francisco Opera, and is given with generous philanthropic support from Mrs Aline Foriel-Destezet, Mrs Susan A. Olde OBE, Simon and Virginia Robertson, Spindrift Al Swaidi, Mercedes T. Bass and Mrs Trevor Swete.

This month’s revival of Graham Vick’s acclaimed production sees Sir John Tomlinson shift roles from Hans Sachs, the selfless cobbler at the centre of the opera to the character of Pogner. During this run Wolfgang Koch will play Sachs, and Sir John speaks with approval of “the natural turning of the pages of the generations. Wolfgang is 20 years younger than me. It’s right that that should happen.”

Sir John sees both roles as key in the story: “Pogner gets the story off the ground by the grandiose act of giving his daughter as the prize for the singing contest on Midsummer’s Day. He spreads goodness and believes in art, in music and the cause of the Meistersingers. On the other hand, Sachs takes a back seat at the beginning – he comes to the fore later. He’s a classic Wagnerian character in that he relinquishes his love of the daughter because he sees that the daughter and Walther, the young knight, are in love. He gives up his own entitlement to her. There’s nothing he’d like more than to marry Eva and have 20 children with her but he sees her and Walther’s love and makes it work out for them, in spite of all the complexities”.

The role is a mammoth undertaking for any singer: “Sachs is on stage for four hours and sings for two and half of those. I think it’s the longest operatic role ever written but probably due to the role’s very personable and human nature, it doesn’t give the impression of overwhelming length.” As such, preparation is key. “It’s a bit like running a marathon,” Sir John says, “It’s a very physically demanding role as a lot of the power comes from the diaphragmatic muscles. They’re important in supporting the sound over a long period of time, which is why a lot of Wagnerians have got that chunky figure. Even a lot of singers who look slim are often very muscular.”

So what is it about Richard Wagner that has inspired Sir John to devote a sizeable part of his career to the composer’s work? “One of Wagner’s great philosophies was that of Gesamtkunstwerk – a total work of art. He wanted a continual dramatic flow and hence the combination of acting and singing. Orchestrally too there’s a lot of fantastic thematic material - leitmotifs. What’s great is that these themes develop along with the characters. The music tells these dramatic stories at deeper levels than often the characters are aware of. It’s very clever and extremely rich.

“For some people there are a lot of political overtones and baggage with Wagner’s work in particular Meistersinger – it was after all Hitler’s favourite piece, I don’t deal with that though, I deal with the piece itself. As a singer that’s what you’re focussed on: the words, the text, the notes, the relationship between the characters. For me, if you play the piece in 1542 I don’t regard the piece as being remotely fascist. There is a hint of nationalism but no more than many operas – Billy Budd for example. Rule Britannia contains a nationalist idea but when we all sing along on the last night of the Proms, we don’t take it very seriously,” then as if to leave no doubt, he says emphatically, “There’s nothing about Meistersinger that upsets me politically or ethically. It’s a wonderful piece because it’s a very sophisticated text. There’s great drama and the music is just glorious – it’s great theatre.”